The invention relates to a particle injector for introducing particles into a carrier flow of a microfluidic system, in particular for injecting biological cells into the carrier flow of a cell sorter, according to the preamble of claim 1.
U.S. Pat. No. 5,489,506 discloses a cell sorter which enables biological cells to be separated dielectrophoretically in a carrier flow, whereby the dielectrophoretic effects used for separating are described for example in MÜLLER, T. et al. : “A 3-D microelectrode system for handling and caging single cells and particles”, Biosensors & Bioelectronics 14 (1999) 247-256. The biological cells to be sorted are hereby injected by a particle injector into the carrier flow, whereby the carrier flow enters the particle injector via an inlet and later leaves it along with the injected biological cells via an outlet. The actual injecting of the biological cells to be sorted takes place through an injection needle, which is stuck through a septum in the particle injector and is guided coaxially into the carrier flow between the inlet and the outlet of the particle injector, so that the cells introduced via the injection needle are carried along by the carrier flow.
The disadvantage to this known particle injector is the loss of cells, arising from cell depositing in the particle injector. In the extreme case these cell deposits can result in clogging of the particle injector, impairing the feed of the carrier flow or to total obstruction. This has a particularly strong effect in fluidic systems with minimal feed rates of e.g. less than 200 μl/h.
The object of the invention therefore is to minimize the loss of cells through particle depositing in the above described known particle injector to prevent obstruction of the particle injector.